Digital-to-analog converters (DACs) are components widely used in data processing systems. There exist various types of DACs, namely weighted current source DACs and resistive DACs. Presently, resistive N-bit DACs are built from a thin film resistor string with 2.sup.N taps. One N-bit DAC stage is cascaded with another P-bit DAC stage, such as described in U.S. Pat. No. 4,543,560 through buffer amplifiers, to extend the conversion capabilities of the N-bit DAC to (N+P)-bits.
The presence of the buffer amplifiers between the two stages impairs the monotonicity of the conversion and increases the conversion time.
Furthermore, the buffer amplifies are space consuming, when the DAC converter is integrated in a chip.